Traditionally, baseband to radio frequency (RF) up-conversion is performed in the analog domain with one of three types of architectures, namely, a heterodyne architecture, a super-heterodyne architecture, or a direct conversion architecture. Analog up-conversion architectures and previous attempts at digital up-conversion architectures have generally been frequency dependent in that they only operate over a small frequency band. In other words, a traditional analog up-converter that is designed for one frequency band will not operate effectively for a different frequency band. For example, an up-converter designed for operation at 800 megahertz (MHz) will not operate properly at 450 MHz, 1.5 GHz, or 1.9 gigahertz (GHz). Therefore, it is not possible for a radio designed for use in one frequency band to be converted for use in an alternate frequency band without physically replacing an up-converter in the radio with a newly designed up-converter for the alternate frequency band or having multiple up-converters each capable of operating in a different frequency band. Either option adds an increase to the cost of a system. Another disadvantage of an analog up-converter is that it is subject to issues related to analog variability such as, but not limited to, component to component variability, temperature variability, voltage variability, and variability due to aging.
A flexible, programmable digital up-conversion system that addresses the issues above is described in commonly owned and assigned U.S. Patent Application Publication No. 2010/0098191 A1, entitled METHODS AND SYSTEMS FOR PROGRAMMABLE DIGITAL UP-CONVERSION, filed on Oct. 20, 2008, and published on Apr. 22, 2010, which is hereby incorporated herein by reference in its entirety.
Further issues arise when up-converting for a concurrent multi-band signal. For instance, while the digital up-conversion system of U.S. Patent Application Publication No. 2010/0098191 A1 can be used for concurrent multi-band signals, it must treat the concurrent multi-band signal as a single wide-band signal. However, due to the large bandwidth of a concurrent multi-band signal, treating the concurrent multi-band signal as a single wide-band signal may exceed or approach processing capabilities of current Application Specific Integrated Circuit (ASIC) and Field Programmable Gate Array (FPGA) technology. Thus, there is a need for a digital up-conversion system for a concurrent multi-band signal that also addresses the other issues discussed above.